Defective DNA ligation during short-patch single-strand break repair in ataxia oculomotor apraxia 1

Reynolds, John J, El-Khamisy, Sherif F, Katyal, Sachin, Clements, Peter, McKinnon, Peter J and Caldecott, Keith W (2009) Defective DNA ligation during short-patch single-strand break repair in ataxia oculomotor apraxia 1. Molecular and Cellular Biology, 29 (5). pp. 1354-1362. ISSN 0270-7306

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Abstract

Ataxia oculomotor apraxia 1 (AOA1) results from mutations in aprataxin, a component of DNA strand break repair that removes AMP from 5' termini. Despite this, global rates of chromosomal strand break repair are normal in a variety of AOA1 and other aprataxin-defective cells. Here we show that short-patch single-strand break repair (SSBR) in AOA1 cell extracts bypasses the point of aprataxin action at oxidative breaks and stalls at the final step of DNA ligation, resulting in the accumulation of adenylated DNA nicks. Strikingly, this defect results from insufficient levels of nonadenylated DNA ligase, and short-patch SSBR can be restored in AOA1 extracts, independently of aprataxin, by the addition of recombinant DNA ligase. Since adenylated nicks are substrates for long-patch SSBR, we reasoned that this pathway might in part explain the apparent absence of a chromosomal SSBR defect in aprataxin-defective cells. Indeed, whereas chemical inhibition of long-patch repair did not affect SSBR rates in wild-type mouse neural astrocytes, it uncovered a significant defect in Aptx(-/-) neural astrocytes. These data demonstrate that aprataxin participates in chromosomal SSBR in vivo and suggest that short-patch SSBR arrests in AOA1 because of insufficient nonadenylated DNA ligase.

Item Type: Article
Schools and Departments: School of Life Sciences > Sussex Centre for Genome Damage and Stability
Subjects: Q Science
Depositing User: Deeptima Massey
Date Deposited: 01 Nov 2012 09:36
Last Modified: 14 Mar 2017 02:07
URI: http://sro.sussex.ac.uk/id/eprint/41092

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